P1568

Code P1568, Cruise System Problem (SPS Indicated High):

Cruise System Circuit:

CIRCUIT DESCRIPTION
The PCM controlled cruise control system is designed to monitor itself to be sure that the desired cruise servo position and actual cruise servo position are equal to each other.

A current DTC P1568 may cause the vehicle to operate in "Power Management" mode and DTC P1599 to set. While in "Power Management," the PCM will shut "OFF" fuel to 3 cylinders to avoid overrevving the engine in case the throttle is being held open by a sticking cruise control throttle cable, brake vacuum release valve, or cruise control servo. "Power Management" may be perceived as a severe engine miss or lack of power.


DTC 1568 WILL SET WHEN:
^ Actual servo position is greater than 15% above desired servo position of 0% for 1 second.

ACTION TAKEN (PCM will default to):
The PCM will not allow cruise control operation with a current DTC P1568 set. The condition that causes the DTC P1568 may also cause the vehicle to operate in "Power Management" and DTC P1599 to be set. DTC P1568 does not illuminate the MIL (Service Engine Soon).

TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
1. Most vacuum solenoids leak a small amount of vacuum when closed. But they should not leak enough to allow the servo to reach WOT in 15 seconds with the vent closed.
2. When the vacuum solenoid is forced "ON" the vacuum will be vented to atmosphere unless the vent valve is stuck closed.


DIAGNOSTIC AIDS
A cruise control throttle cable which binds or intermittently sticks can cause DTC P1568 to set. DTC P1568 can also be set by manually compressing the cruise servo to raise engine speed.

Outside interference such as a CB antenna lead near the PCM wiring harness may induce a false SPS signal and set DTC P1568.

An intermittent may be caused by a poor connection, rubbed through wire insulation, or a wire broken inside the insulation.

Check for:
^ Poor connection or damaged harness - Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection, and damaged harness.